586 REV. E. HILL ON WELLS IN WTIST SUFFOLK UOULDEK-CLAY. 



perfectly diy until a full of snow. When this melted and filled it, 

 the water stood tliere day after day till it disappeared by evapora- 

 tion. But then, this clay being thus impervious, the question arises, 

 how does the rainfall find its way down to the water-bearing 

 seams ? In the Geol. Surv. Mem. on quarter-sheet 51 8.E. (lb86), 

 which includes the west boundary of this parish *, it is said that 

 *' owing to the boulders and stones it [the clay] contains, and also 

 to occasional seams of sand, wells are often made in it and a fair 

 supply of water obtained." But the boulders and stones do not 

 make it pervious : 5'et these sand-seams must obtain their water 

 from the surface. I conclude then that this Boulder-clay is not an 

 uniform homogeneous mass ; it must contain seams or beds of 

 gravel and sand, and these must rise to the surface, or in some way 

 communicate with it. 



This conclusion was altogether contrary to my preconceived 

 ideas. I knew that many geologists regarded this Boulder-clay as 

 formed beneath a glacier by the friction of a mass forced forward 

 over its bed. I expected therefore to find a clay perfectly imper- 

 vious to water, and with any appearance of bedding which it 

 might present parallel to the direction of motion. I have looked 

 attentively at all visible sections. Those in the immediate neigh- 

 bourhood are oi^ly such as ditches can give. They showed pockets 

 and patches containing sand or silt of irregular and fantastic shapes, 

 and though, by reason of denudation, it is probable that this is no 

 superficial structure, they are necessarily very limited and unsatis- 

 factory. As yet I have been able to examine more extensive 

 sections only in two localities, namely. Bury St. Edmund's, seven 

 miles to the N.N.W., and Sudbury, ten miles to the S^ Near 

 Bury, just beyond Horringer (Horningsheath) Bed House, a large 

 pit in the fields shows about 8 feet of Eoulder-clay resting on 

 gravel, and below the gravel, chalk. Here then we have the base 

 of the Clay shown for several hundred yards. It is typical Boulder- 

 clay of a reddish colour, full of chalk and flints. But in the middle, 

 at my first visit in Nov. 1890, was a mass about 12 yards long clearly 

 distinguished by its bluish tint from the rest ; on one side it 

 abutted against this vertically, on the other overlay it obliquely. At 

 Sudbury Boulder-clay is seen in several pits, one of which contains the 

 remarkable mass described by Mr. Marr in the Geol. Mag. foi: 1887 

 (p. 262). The best section is that in the Ballingdon Brick-yards, 

 across the river, about half a mile N.W. of the Sudbury Railway 

 Station. Here, below the thin surface-soil, is some 10 feet of yellow 

 Boulder-clay, in which a sandy streak, visible at some distance, 

 runs for several feet horizontally, then turns up and bends back 

 till it reaches the surface. Below the clay is from 12 to 20 feet of 

 much contorted stratified gravel. This lies on the irregular surface 

 of a second Boulder-clay, very dark in its upper portion, but light 

 with dark patches below, and containing irregular patches and 

 scams of yellow sandy clay. About 20 feet of this lower mass was 



* Cockfield is mainly included in quarter-sheet 50, S.W. The memoir on 

 this map was published in 1881. 



